Republicans have signalled their opposition to Barack Obama's multibillion dollar jobs plan, even before he was due to unveil it in a crucial speech to a joint session of Congress.

Republican members of Congress said on Thursday morning that, based on leaks to the media, there was nothing new in the speech, which would be just a rehash of proposals Obama has put forward since his days on the campaign trail in 2008.

Some Republican members even announced publicly they intend to boycott the speech, a rare snub for a sitting president.

The Republican leader in the Senate, Mitch McConnell, dismissed Obama's jobs plans as retreads. "What is surprising is the president's apparent determination to apply the same government-driven policies that have already been tried and failed," he said in a speech to the Senate.

'"The definition of insanity, as Albert Einstein once famously put it, is to do the same thing over and over again and expect a different result. Frankly, I can't think of a better description of anyone who thinks the solution to this problem is another stimulus. The first stimulus didn't do it. Why would another one?"

He added: "This isn't a jobs plan. It's a re-election plan."

Obama's proposals, which will cost at least $300bn, include about $100bn in spending on construction of roads, bridges and other huge infrastructure projects as well as extra cash for states to prevent teachers, police and others being laid off.

He is also proposing an extension of a payroll tax cut due to expire at the end of the year, an extension of unemployment benefit, and more training and subsidies for the long-term unemployed.

The jobs plan is part of Obama's attempt to reverse a rapid drop in the polls because of the 9.1% unemployment rate, up from the 7.8% when he took office in January 2009. A Gallup poll this week gave the president an approval rating of only 42%, perilously low for a president seeking re-election next year.

Even though speeches by a president to a joint session of Congress are relatively rare, such is the polarisation in Washington that many Republicans said they intended to boycott it rather than participate in what they see as an election gimmick.

The Republican Speaker, John Boehner, at a press conference in Congress on Thursday, urged his House colleagues not to mount a boycott, saying it would be disrespectful of the president.

But Republican congressman Joe Walsh said speeches by the president at joint sessions of Congress should be saved for special occasions. It was time for action, not speeches. "You can't lead this country by speeches," Walsh said in an interview with CNN.

The unhappiness of many Republicans is shared on the other side, with Democrats regarding Obama's proposals as too timid and seeking a much more ambitious stimulus package.

Almost all of Obama's plans require congressional approval and he is to send the proposals to the Hill next week, setting up a third major clash with Republicans this year. A standoff between Republicans and the White House before the summer recess over the debt crisis left Washington paralysed for weeks, while earlier this year Republicans threatened to close down the federal government.

House Republicans, reluctant to be cast as the villains, were in public unwilling to dismiss Obama's plans out of hand.

Boehner, at the press conference, said: "I'm hopeful that after the president gives his speech that we'll be able to sit down, in a bipartisan way, and find common ground that will help improve our economy, and improve the job picture for the American people."

But behind the scenes, House Republicans, who voted against Obama's first stimulus package and see little reason to vote for a second, were sceptical.

A Republican congressional source said that if the president had been genuine about seeking a bipartisan approach he would have consulted them beforehand. The source said Boehner had written to the White House asking for a meeting this week but had not received a reply.

If, as the White House expects, the Republicans boycott his speech, Obama is planning to go out on the road in the months ahead portraying his opponents as obstructionist.

The president is to hold the first of a series of meetings on jobs in Richmond, Virginia, on Friday.